I have purchased a 2002 Mercedes Sprinter 316 CDI van with a six-speed Sprintshift gearbox. As I can't find any way to check the oil level in the gearbox I was wondering if they were sealed for life, ...

This is an increasingly common problem for people who carry big loads and especially for those who tow heavy trailers. In some cases, as you've discovered, it's very easy to get perilously close to ...